This modified in situ model study will evaluate the mode-of-action of an experimental dentifrice containing stannous fluoride to occlude tubules compared to a regular fluoride dentifrice and a negative control (mineral water). The study treatments will be administered for a total of 10 days, with participants wearing two appliances in their mouth that will hold samples of dentine. The dentine samples will be examined after 1, 4, 8 and 10 days of treatment using scanning electron microscopy (SEM) and the resulting images graded for the amount of occlusion. In addition, the robustness of any occlusion generated by the treatments will be tested by exposing the dentine samples to an acid challenge (orange juice) after 9 and 10 days treatment.